 /*******************************************************************************
  * Copyright (c) 2004, 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.internal.presentations.util;

 import org.eclipse.jface.util.Geometry;
 import org.eclipse.swt.graphics.Point;
 import org.eclipse.swt.graphics.Rectangle;
 import org.eclipse.swt.widgets.Control;
 import org.eclipse.ui.internal.dnd.DragUtil;
 import org.eclipse.ui.presentations.StackDropResult;

 /**
  * @since 3.0
  */
 public class ReplaceDragHandler extends TabDragHandler {

     private final class DragCookie {
         int insertPosition;

         public DragCookie(int pos) {
             insertPosition = pos;
         }
     }

     private AbstractTabFolder tabFolder;

     public ReplaceDragHandler(AbstractTabFolder folder) {
         this.tabFolder = folder;
     }
     
     /* (non-Javadoc)
      * @see org.eclipse.ui.internal.presentations.util.TabDragHandler#dragOver(org.eclipse.swt.widgets.Control, org.eclipse.swt.graphics.Point)
      */
     public StackDropResult dragOver(Control currentControl, Point location,
             int dragStart) {

         // Determine which tab we're currently dragging over
 //Point localPos = tabFolder.getControl().toControl(location);

         AbstractTabItem tabUnderPointer = tabFolder.getItem(location);

         // This drop target only deals with tabs... if we're not dragging over
 // a tab, exit.
 if (tabUnderPointer == null) {
             Rectangle titleArea = tabFolder.getTabArea();

             // If we're dragging over the title area, treat this as a drop in the last
 // tab position.
 if (titleArea.contains(location) && tabFolder.getItemCount() > 0) {
                 int dragOverIndex = tabFolder.getItemCount();
                 AbstractTabItem lastTab = tabFolder.getItem(dragOverIndex - 1);

                 // Can't drag to end unless you can see the end
 if (!lastTab.isShowing()) {
                     return null;
                 }
                 
                 // If we are unable to compute the bounds for this tab, then ignore the drop
 Rectangle lastTabBounds = lastTab.getBounds();
                 if (lastTabBounds.isEmpty()) {
                     return null;
                 }

                 if (dragStart >= 0) {
                     dragOverIndex--;

                     return new StackDropResult(lastTabBounds, new Integer (
                             dragOverIndex));
                 }

                 // Make the drag-over rectangle look like a tab at the end of the tab region.
 // We don't actually know how wide the tab will be when it's dropped, so just
 // make it 3 times wider than it is tall.
 Rectangle dropRectangle = titleArea;

                 dropRectangle.x = lastTabBounds.x + lastTabBounds.width;
                 dropRectangle.width = 3 * dropRectangle.height;
                 return new StackDropResult(dropRectangle, new Integer (
                         dragOverIndex));

             } else {
                 // If the closest side is the side with the tabs, consider this a stack operation.
 // Otherwise, let the drop fall through to whatever the default behavior is
 Rectangle displayBounds = DragUtil.getDisplayBounds(tabFolder.getControl());
                 int closestSide = Geometry.getClosestSide(displayBounds, location);
                 if (closestSide == tabFolder.getTabPosition()) {
                     return new StackDropResult(displayBounds, null);
                 }
                 
                 return null;
             }
         }

         if (!tabUnderPointer.isShowing()) {
             return null;
         }
         
         Rectangle tabBounds = tabUnderPointer.getBounds();
         
         if (tabBounds.isEmpty()) {
             return null;
         }

         return new StackDropResult(tabBounds, new DragCookie(tabFolder
                 .indexOf(tabUnderPointer)));
     }

     /* (non-Javadoc)
      * @see org.eclipse.ui.internal.presentations.util.TabDragHandler#getInsertionPosition(java.lang.Object)
      */
     public int getInsertionPosition(Object cookie) {
         if (cookie instanceof DragCookie) {
             return Math.min(tabFolder.getItemCount(),
                     ((DragCookie) cookie).insertPosition);
         }

         return tabFolder.getItemCount();
     }

 }

